Tidal generator

ABSTRACT

The present invention relates to an electric power generator apparatus that generates electrical power from the tidal movements of a body of water by employing multiple energy producing systems. Those energy producing systems include: (1) a moveable tank system associated with hydraulic cylinders in which the upward and downward movements of the tank relative to the tide are used to generate electrical power; (2) an enclosure system in which the controlled inflow and outflow of water between the enclosure and the surrounding body of water is used to generate electrical power; (3) a bellows system in which the effects of the tidal movements are used to force water from the bellows tank through a generator thereby producing electrical power; and (4) a buoyant mass-actuated piston system in which the movement of floating objects (such as docked ships) relative to the tide is used to generate electrical power.

The present application is a continuation-in-part of patent application08/209,870 filed on Mar. 11, 1994, now U.S. Pat. No. 5,426,332.

BACKGROUND OF THE INVENTION

During the past three decades, the cost of fossil fuels has increaseddramatically. Moreover, in recent years, scientists have begun torecognize the environmentally detrimental effects of hydrocarbonemissions associated with the use of fossil fuels. These factors havelead to increased interest in renewable and environmentally safe formsof energy production including photoelectricity, solar thermal energy,geothermal energy, wind power and hydroelectricity.

Hydroelectric power has been the most widely exploited form of"alternate" energy production. Tides have been harnessed to generatepower for hundreds of years. For example, tidal mills on the Danuberiver date back to the twelfth century. More recently, energytechnologists have employed various tidal power station designs togenerate and store electrical energy. Many of these designs have beenproblematic because of adverse effects on the environment such asflooding and changing the tidal regime, which leads to disruption offragile seashore and estuary ecosystems. See, e.g., F. O'Kelly,"Harnessing the Ocean's Energy" Are We Ready for a Gift from the Sea?,Hydro-Review, Vol. X, No. 4, July 1991!. Many designs are not amenableto large-scale deployment and, therefore, cannot produce commerciallymeaningful quantities of electrical energy in a cost effective manner.Moreover, many proposed tidal power station designs rely on a singlemechanism for generating energy, which may result in energy productionthat is out of phase with consumer demands as well as dramatic reductionof energy output under certain weather conditions or if repairs to thestation are required. See, e.g., Kertzman, U.S. Pat. No. 4,249,085!.

It would therefore be desirable to provide an apparatus for generatingelectrical energy from the tidal movements of a body of water that isnot limited to a narrow range of feasible installation sites and that iswell-suited for deployment in many different locations because it willnot effect fragile seashore and estuary ecosystems.

It would also be desirable to provide an apparatus for generatingelectrical energy from the tidal movements of a body of water that doesnot flood surrounding lands or markedly change the tidal regime.

It would also be desirable to provide an apparatus for generatingelectrical energy from the tidal movements of a body of water that isamenable to large-scale deployment and that produces significantquantities of electrical energy.

It would also be desirable to provide an apparatus for generatingelectrical energy from the tidal movements of a body of water that canproduce energy over the entire 12 hour and 25 minute tidal cycle.

It would also be desirable to provide an apparatus for generatingelectrical energy from the tidal movements of a body of water thatemploys multiple interactive mechanisms that optimize the quantity ofelectrical energy production.

It would also be desireable to provide an apparatus for generatingelectrical energy from the tidal movements of a body of water that maybe installed in segments.

SUMMARY OF THE INVENTION

It is an object of this invention to provide an apparatus for generatingelectrical energy from the tidal movements of a body of water that isnot limited to a narrow range of feasible installation sites and that iswell-suited for deployment in many different locations because it willnot effect fragile seashore and estuary ecosystems.

It is also an object of this invention to provide an apparatus forgenerating electrical energy from the tidal movements of a body of waterthat does not flood surrounding lands or markedly change the tidalregime.

It is also an object of this invention to provide an apparatus forgenerating electrical energy from the tidal movements of a body of waterthat is amenable to large-scale deployment and that produces significantquantities of electrical energy.

It is also an object of this invention to provide an apparatus forgenerating electrical energy from the tidal movements of a body of waterthat can produce energy over the entire 12 hour and 25 minute tidalcycle.

It is also an object of this invention to provide an apparatus forgenerating electrical energy from the tidal movements of a body of waterthat employs multiple interactive mechanisms that optimize the quantityof electrical energy production.

It is also an object of this invention to provide an apparatus forgenerating electrical energy from the tidal movements of a body of waterthat may be installed in segments.

In accordance with the foregoing objects of the present invention, weprovide an apparatus for generating electrical energy from the tidalmovements of a body of water. The present invention comprises a tidalelectric power generator that employs multiple interactive energyproducing systems that cooperate to enhance the overall output andreliability of the generator. Those energy producing systems include:(1) a moveable tank system associated with hydraulic cylinders in whichthe upward and downward movements of the tank relative to the tide areused to generate electrical power; (2) an enclosure system in which thecontrolled inflow and outflow of water between the enclosure and thesurrounding body of water is used to generate electrical power; (3) abellows system in which the effects of the tidal movements are used toforce water from a bellows tank through a generator thereby producingelectrical power; and (4) a buoyant mass-actuated piston system in whichthe movement of floating objects (such as docked ships) relative to thetide is used to generate electrical power. The use of these multipleinteractive energy producing systems maximizes the electrical poweroutput of the tidal generator relative to the area that the generatoroccupies.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-cited and other objects and advantages of the presentinvention will be apparent upon consideration of the following detaileddescription, taken in conjunction with the accompanying drawings, inwhich reference characters consistently refer to the same elements, andin which:

FIG. 1 is a schematic view of one embodiment of the present invention inwhich an enclosure system, a moveable tank system and a bellows systemare employed to generate electrical energy;

FIG. 1a is a more detailed schematic view of the inlet and outlet valvesused with the enclosure system;

FIG. 2 is a schematic view of another embodiment of the presentinvention in which an enclosure system and a moveable tank system areemployed to generate electrical energy;

FIG. 3 is a schematic view of another embodiment of the presentinvention in which an enclosure system and a bellows system are employedto generate electrical energy;

FIG. 4 is a schematic view of another embodiment of the presentinvention in which a moveable tank system and a bellows system areemployed to generate electrical energy; and

FIG. 5 is a schematic view of a buoyant mass-actuated piston system thatmay be used in conjunction with the apparatus shown in FIGS. 1-4 togenerate electrical energy.

DETAILED DESCRIPTION OF THE INVENTION

The tidal power generator of the present invention includes threeprimary systems for producing electrical energy: (1) the moveable tanksystem 100; (2) the enclosure system 200; and (3) the bellows system300. The moveable tank system 100 includes a hollow tank 10 that issuspended in a rigid support structure 11. The tank 10 is attached tothe rigid support structure 11 using one or more telescoping hydrauliccylinders 12. The top and the bottom of the tank 10 are equipped with aseries of valves 13 that allow for controlled flow of water and air intoand out of the tank 10.

In operation, the telescoping hydraulic cylinders 12 permit controlledvertical movement of the tank 10 within the rigid support structure 11,and may lock the tank 10 in place at a predetermined location relativeto the tide level. Preferably, the height of the tank 10 isapproximately equal to the maximum tidal range (i.e, the maximumdifferential between the extreme high tide and the extreme low tidelevels) and the rigid support structure 11 is at least three times theheight of the maximum tidal range. Thus, the tank 10 may travel so, atone time, its bottom rests just below the high tide mark, and at anothertime, the top of the tank 10 is submerged just below the low tide mark.

Electrical energy is generated by the movement of the tank 10 duringboth the rising and the lowering of the tide as follows. The tank 10 isinitially empty and sits above the high tide level. As the high tideapproaches, valves 13 located in the top and bottom of the tank 10, areopened and the tank 10 is allowed to settle into the water. As waterflows into the tank 10, the tank 10 submerges until the top of the tank10 is substantially flush with the high tide level. The valves 13 arethen closed and the telescoping hydraulic cylinders 12 lock the tank 10at this position. One skilled in the art will recognize that thehydraulic cylinders 12 may be locked into position using any type oflocking mechanism 18 including manually operated, computer-controlled orautomatic resistance mechanisms that arrest movement of the tank at adesired point relative to the tide level.

As the high tide recedes to low tide, the tank 10 remains filled withwater and is suspended above the low tide level. The weight of the waterin the tank 10 exerts a large downward force and causes the hydraulicfluid within the cylinders 12 to be subject to high-pressure conditions.

At approximately the time of low tide, the hydraulic cylinders 12 areunlocked and the tank 10 is allowed to settle into the water to a levelat which the top of the tank 10 is substantially flush with the low tidelevel. As the tank is lowered into the water, the hydraulic cylinders 12deliver high-pressure hydraulic fluid to be stored in one or morehydraulic accumulators 14. That fluid is subsequently deliveredgradually through a turbine generator 15 whereby electrical energy isproduced. The operation of the accumulator 14 and the generator 15 aredetailed below.

The valves 13 are next opened and a small amount of stored hydraulicenergy is expended to lift the tank 10 out of the water as the watergradually drains out of the tank 10. When the tank 10 is substantiallydrained and positioned with its bottom substantially flush with the lowtide level of the water, the valves 13 are closed and the hydrauliccylinders 12 are again locked to maintain the tank 10 in this position.

As the tide rises, the substantially empty tank 10 exerts a large upwardforce due to buoyancy. At approximately the high tide, the tank 10 isallowed to rise out of the water with the hydraulic cylinders 12controlling its rate of ascent. During this ascent the hydrauliccylinders 12 gather high-pressure hydraulic fluid for storage and laterconversion to electrical energy. The tank 10 is then locked intoposition with its bottom just below the high tide level, thus completingone cycle of tidal rising and lowering.

One skilled in the art will recognize that several types of hydraulicaccumulators may be used with the present invention. For example, thehydraulic accumulator 14 may be the type that employs compressed air orthe type that uses a cylinder with a large weight for maintainingpressure during storage. similarly, several types of turbines may beemployed with the present invention. The turbines may be, for example,gear pump-type turbines or design impulse-type turbines in whichmultiple buckets catch the hydraulic fluid as it is released fromnozzles associated with the accumulator. Electrical power generated bythe turbines is transported to land utilities via cable 20 along thefloor of the body of water.

The moveable tank system 100 allows for gradual delivery of storedhydraulic pressure fluid from accumulators 14 through turbine generators15.

Thus, electrical power may be produced continuously or on demand overthe 12 hour and 25 minute tidal cycle, depending on consumerrequirements.

It will be readily apparent to the skilled worker that one large tank orseveral smaller tanks may be employed in the moveable tank system 100.In some applications, the use of several smaller tanks may be preferablebecause water can be released from the tanks sequentially or in groups,thereby enhancing control over the amount of water released at any giventime.

The enclosure system 200 includes a barrier that is formed bysubstantially vertical walls 16. The vertical walls 16 extend above theextreme high tide level and below the extreme low tide level. Theenclosure system 200 also includes a solid, substantially horizontalbottom 17 that is joined to the vertical walls 16 below the extreme lowtide level. The vertical walls 16 and horizontal bottom 17 are formedfrom a durable material such as structural concrete and are firmlyrooted in the floor of the ocean (or other body of water in which thepresent invention is deployed).

The vertical walls 16 and horizontal bottom 17 form a large basin withinwhich water is allowed to flow to and from the surrounding ocean througha series of electrical energy-generating turbines 19. The turbines 19are associated with openings in the vertical walls 16. Those openingsdirect water moving into the basin from the surrounding body of waterand water moving out of the basin to the surrounding body of waterthrough the turbines 19. Such "double action" water flow is accomplishedby: (1) placing the turbines 19 longitudinally inside the wall 16 and(2) connecting both the inlet and the outlet of the turbines 19 to twogate valves 21 each. One gate valve opens to the inside of the basin andthe other opens to the surrounding body of water.

In this way, power may be generated during low tide by releasing waterthrough the turbines 19 as the inside inlet valve 21a and the outsideoutlet valve 21b are opened and water moves from the inside of the basinto the surrounding body of water. At high tide, power may be generatedby releasing water through the turbines 19 as the outside inlet valve21c and the inside outlet valve 21d are opened and water moves into thebasin from the outside body of water. Moreover, because the release ofwater from the basin corresponds to the maximum difference between thehigh tide and low tide levels (i.e., the "head") the discharge of waterhas a negligible effect on the tidal regime.

The turbines 19 deployed longitudinally within the walls 16 of theenclosure system 200 may be any of several types of turbines well knownto those skilled in the art, including bulb-type axial flow turbines,thru-flow axial flow turbines, and turbines connected to a hydraulicpump. Depending on the type of turbine used, electrical power may beproduced directly and transported by cable to land utilities, or highpressure hydraulic fluid may be stored in accumulators prior toconversion.

The bellows system 300 includes a substantially hollow stationary tank22 that is, preferably, positioned below the horizontal bottom 17 of theenclosure system 200. Also, preferably, the stationary tank 22 isaffixed to the floor of the body of water. A bellows tank 23 consistingof a flat lid 24 and compressible and expandable side walls 25 that forma bellows is connected to the top of the stationary tank 22. The bellowstank 23 is equipped with a side support structure 26 to prevent collapseand damage from currents and other phenomena that may cause horizontalmovement of the bellows. In the embodiments of the present inventionthat employ the bellows system 300 in conjunction with the enclosuresystem 200, the horizontal bottom 17 of the enclosure is adapted withvents that allow water to flow through the bottom 17 of the enclosure.In this way, the bellows system 300 is subject to the higher pressure ofhigh tide and reduced pressure of low tide.

In alternate embodiments of the present invention, the bottom 17 of theenclosure may be contiguous with the floor of the body of water, or maybe the floor itself. In such embodiments, the bellows system 300 isaffixed to (and above) the bottom of the enclosure, where it is subjectto the higher pressure of high tide and the reduced pressure of lowtide.

The volume of the bellows tank 23 and the volume of the stationary tank22 are approximately equal. No part of either the bellows tank 23 orstationary tank 22 extends above the low tide level.

An air inlet 27 extends from the stationary tank 22 to a point above thesurface of the water. The air inlet 27 provides the stationary tank withan air supply and maintains that air substantially at atmosphericpressure.

In operation, the bellows tank 23 is initially filled with water. Athigh tide the bellows is substantially deflated and emptied of water.Upon deflation, a valve positioned in an opening that connects thestationary tank 22 to the bellows tank 23 is opened and the waterinitially kept within the bellows tank 23 moves into the stationary tank22. As the water flows from the bellows tank 23 into the stationary tank22 it passes through a turbine generator 28 thereby producing electricalenergy.

At low tide, the water in the stationary tank 22 is pumped back into thebellows tank 23. A portion of the energy produced during the deflationof the bellows is used for this reinflation. There is, however, a netenergy gain because reinflation is accomplished at low tide. Typically,electrical power is produced directly by the turbine generator 28 as thebellows tank is deflated, and that power is transported by cable 20 toland utilities.

It will be readily apparent to the skilled worker that one large bellowstank 23 and stationary tank 22 arrangement or several smallerarrangements may be employed in the bellows system 300. In someapplications, the use of several smaller bellows/stationary tanks may bepreferable because smaller bellows are easier to maintain and are lessprone to damage. In order to maximize its efficiency, the bellows tanksystem is preferably deployed at a depth of about 120 meters or less.

The skilled worker will readily appreciate that the bellows tank is notnecessarily configured as a collapsible "accordion" structure. Astructure of any configuration that allows water to be delivered to thestationary tank is acceptable for use with the present invention. In analternate embodiment, the submerged stationary tank may be deployedwithout a bellows tank-type structure. The stationary tank can beoperated to allow selectively water to travel into and out of the tank,to and from the surrounding body of water, so that the stationary tankis substantially filled with water at high tide and substantially filledwith air at low tide. The stationary tank may be adapted with a filtermeans that will prevent debris from the body of water from entering thesubmerged stationary tank and disrupting the operation of the turbines.

The present invention employs interactive electrical energy producingsystems--the moveable tank system 100, the enclosure system 200 and thebellows system 300--that cooperate to enhance the overall output of thepresent invention. The use of multiple systems increases the reliabilityof the tidal generator. For example, even if storm conditions or highwinds interfered with the operation of the moveable tank system 100, theenclosure system 200 and the bellows system 300 would continue toproduce electrical power. Moreover, the use of multiple systems insuresenergy production when repairs to one of the systems are required,allows for installation of the power station in segments and allows foruse of the individual energy producing systems when demand levels arereduced or environmental conditions would so require.

The present invention is amenable to large scale deployment andproduction of significant quantities of electrical energy yet iscircumnavigable and does not significantly disrupt marine habitats.

Preferably, the basin formed by the vertical walls 16 and the horizontalbottom 17 of the enclosure system has a surface area of at least 4,000m². The large basin size accommodates the upward and downward movementof the one or more large moveable tanks into and out of the water withinthe basin. While it is preferable to deploy the moveable tank(s) so thatthey travel vertically within the area defined by the vertical walls ofthe enclosure, it may also be advantageous under some circumstances todeploy the moveable tanks around the outer perimeter of the enclosure.

Preferably, the bottom of the enclosure is large enough to accommodatethe bellows/stationary tank(s) completely beneath it. This wouldminimize the environmental impact of the tidal generator, reduce wearand tear on the bellows and facilitate repairs to the bellows. The samebenefits will accrue in the embodiments of this invention where thebottom 17 of the enclosure is contiguous with the floor of the body ofwater (or is the floor itself), as the vertical walls 16 of theenclosure can be constructed to completely surround the bellows system300.

Preferably, the tidal electric power generator of the present inventionis deployed in an ocean environment in which there is a large differencebetween the high tide and the low tide levels. Large tide differentialwill enhance the output of the tidal generator. The large-scale andsturdy design of the present invention makes it suitable for deploymenta significant distance off shore where it will not interfere withdelicate shoreline ecosystems. The tidal generator of the present systemmay also be deployed in certain river, bay, sea, estuary or lakeenvironments.

The embodiment of the present invention shown in FIG. 1 may be modifiedto include additional or fewer energy producing systems depending oneconomic, environmental or other considerations. For example, FIG. 2shows an embodiment of the present invention comprising the moveabletank system 100 and enclosure system 200. This embodiment may bepreferable where it is impractical to deploy a bellows system 300 or tosupport the bottom of the enclosure system above the floor of the bodyof water.

FIG. 3 shows another embodiment of the present invention comprising theenclosure system 200 and the bellows system 300. This embodiment may bepreferable in environments where it is desireable to limit the height ofthe tidal generator. An enclosure system situated directly atop thebellows system (where the submerged stationary tank is deployed eitherwith or without the bellows tank) appears to be the most efficient andcost-effective configuration of the present invention. The efficiency ofthis configuration can be further enhanced by using electrical energygenerated by the enclosure system to power the consumptive phase inwhich water is pumped out of the submerged stationary tank.

FIG. 4 shows another embodiment of the present invention comprising themoveable tank system 100 and the bellows system 300. This embodiment maybe preferable for deployment in environments where construction of theenclosure system 200 would unduly interfere with the flow of thesurrounding body of water.

FIG. 5 shows a buoyant mass-actuated piston energy producing system 400that may be used in conjunction with any of the embodiments of thepresent invention shown in FIGS. 1-4. The buoyant mass-actuated pistonsystem includes a support arm 29 that may be affixed to and horizontallyextend from the rigid support structure 11 of the moveable tank system100 or the top of the vertical walls 16 of the enclosure system 200. Thesupport arm 29 is connected to a hydraulic cylinder 30 similar to thatused with the moveable tank system 100. A sling 31 capable of cradling abuoyant object 32 such as a docked ship is attached to the hydrauliccylinder 30.

In operation, the cradled buoyant object 32 is locked into position athigh tide and is lowered as the tide approaches its lowest level. Thedownward force exerted by the object 32 causes the hydraulic fluid inthe cylinder 30 to be subject to high-pressure conditions. As the object32 settles into the low tide level water, the hydraulic cylinder 30delivers high-pressure hydraulic fluid to accumulators for temporarystorage until turbines are used to generate power from the storedhydraulic fluids. The force generated by the upward movement of thebuoyant object during rising tides may also be used to pressurize thehydraulic fluid within the cylinder 30 for ultimate conversion toelectric power.

The skilled worker will recognize that the buoyant mass-actuated pistonsystem 400 may share accumulators and generators with the moveable tanksystem, or the buoyant mass-actuated system may be equipped with its ownaccumulators and generators. Preferably, embodiments of the presentinvention that incorporate the buoyant mass-actuated piston system 400will employ multiple units of the system in order to maximize energyproduction.

The apparatus of the present invention is advantageous in that it can bereadily employed for "pumped storage" of electrical energy. Thedisclosed apparatus may be adapted to generate electrical energy attimes that coincide with peak demand hours for energy consumption. Mostcurrently known pumped storage units consume more energy than theyproduce. However, the present invention can operate as anenergy-positive pumped storage unit because of the constant availabilityof energy from tidal movements.

The disclosed tidal generator can also be used to produce industrial-usegasses such as hydrogen gas and oxygen gas. During times when surpluselectrical energy is generated by the apparatus of the presentinvention, that energy can be used to react with water. Such a reactionresults in the production of oxygen and hydrogen gasses. The tidal powerstation can be equipped with well-known processing facilities toseparate and store the resulting hydrogen and oxygen gasses. Moreover,pipelines running between the tidal power station and the shoreline canbe constructed to accommodate delivery of the gasses for use in variousindustrial applications.

The skilled worker will appreciate that the present invention can bepracticed by other than the described embodiments, which are presentedfor purposes of illustration and not of limitation, and the presentinvention is limited only by the claims that follow.

We claim:
 1. An apparatus for generating electrical energy from thetidal movements of a body of water having a tidal regimen and a floorcomprising:an enclosure securely fixed to the floor of the body ofwater, the enclosure being formed by substantially vertical walls and asubstantially horizontal bottom wherein the walls extend above theextreme high tide level and below the extreme low tide level of the bodyof water, and the walls are adapted with means for selectively directingwater to flow into and out of the enclosure through turbines operativelyassociated with the walls and wherein the apparatus is operable todirect the flow of water into or out of the enclosure so as toselectively allow a difference between the height of the water insidethe enclosure and the height of the water outside of the enclosure toexist; and wherein the apparatus is operable to selectively direct thewater to flow into or out of the enclosure at intervals where adifference in the height of the water inside the enclosure and theheight of the water outside the enclosure exists.
 2. An apparatusaccording to claim 1 that is deployed in an off-shore location.
 3. Anapparatus according to claim 1 wherein the apparatus is operable toselectively direct the flow of water into or out of the enclosure atintervals of the tidal regimen at which the difference in the height ofthe water inside the enclosure and the height of the water outside theenclosure substantially approximates the greatest difference between thewater levels at high tide and low tide.
 4. An apparatus for generatingelectrical energy from the tidal movements of a body of water havingtides and a floor comprising:an enclosure securely fixed to the floor ofthe body of water, the enclosure being formed by substantially verticalwalls and a substantially horizontal bottom wherein the walls extendabove the extreme high tide level and below the extreme low tide levelof the body of water, and the walls are adapted with means forselectively directing water to flow in and out of the enclosure throughturbines operatively associated with the walls; at least one stationarytank that is positioned entirely below the extreme low tide level of thebody of water, wherein the stationary tank is adapted with means toselectively allow water to travel between the stationary tank and thesurrounding body of water so that the stationary tank is substantiallyfilled with water at high tide and substantially filled with air at lowtide; a turbine means operatively associated with the stationary tankthat generates power as water moves from the surrounding body of waterinto the stationary tank; and a means for supplying air to thestationary tank so that the pressure of the air maintained within thestationary tank is substantially equal to atmospheric air pressure;wherein water is directed out of the stationary tank at substantiallythe time of low tide when the body of water exerts comparatively lesspressure on the stationary tank, and wherein water is directed into thestationary tank at substantially the time of high tide when the body ofwater exerts comparatively greater pressure on the stationary tank, soas to accomplish a net gain of power from the selective travel of thewater into and out of the stationary tank.
 5. An apparatus according toclaims 1 or wherein the substantially horizontal bottom is the floor ofthe body of water.
 6. An apparatus according to claims 1 or 4 comprisinga plurality of means for selectively directing water to flow into andout of the enclosure through turbines operatively associated with thewalls, each of said means being positioned between the extreme high tidelevel and extreme low tide level of the body of water.
 7. An apparatusaccording to claim 4 that is deployed in an off-shore location.